Recently, there appears an integrated circuit (LSI) loading plural cells on a single chip. In the integrated circuit of this kind, there is such a problem that the electric power consumption increases due to the increase of the circuit scale. Therefore, it is considered to decrease the voltage supplied to the integrated circuits which are not used, thereby achieving conservation of electric power.
When the voltage supplied to the integrated circuit is decreased, there is a case that the flip-flop circuits arranged in the integrated circuit are required to hold the data stored inside. Therefore, it is conceived that the power supplies are separately provided for the flip-flop circuits required to hold the data and the cells other than those flip-flop circuits (See. Japanese Laid-open Patent Applications No. 2006-210841 and No. 2005-157487).
However, when the power supplies are separately provided as described above, the number of the power supplies increases, and there is an anxiety that the chip size increases.